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Post by mutley on Nov 19, 2009 15:55:09 GMT
If Dickdastardly40 doesnt know I bet there are more who dont know as well.
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Post by Deleted on Nov 19, 2009 16:45:13 GMT
Just to add to this debate about hydraulic testing of shells, if you look back a bit on this thread, you'll see that I tested my combustion chamber to over 20 lb without observing any movement, but perhaps it was OK 'cos of all those rivets.....
JB
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Post by mutley on Nov 19, 2009 17:25:23 GMT
You pump away if you want JB.
Ive seen boilers stay dry at 50psi and leak like sieves at 80psi. The only test that proves anything will be the 2x and again I've seen boilers go to 19mins dry as a bone and then form a pin head leak at 20 mins.
That will then be down to the discretion of your boiler tester. Some will let it go, some wil fail it and I know testers in each catagory.
Andy
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Post by Deleted on Nov 23, 2009 18:46:11 GMT
Back on the Boil!Paul the boiler inspector is visiting on Thursday (bringing extra heat), to help me put in the bushes and ensure that the foundation ring fitment is sound. I thought that drilling and tapping the dome bush before brazing would be a good idea, together with the cap. However, the drawing specifies only 12 scabby little 6BA countersunk mild steel screws to hold it down, and once again, the doom mongerers at the club say it'll leak unless you groove the bush etc..... So, I figured that 24 HT Steel 2mm x 6mm button head screws would do a better job, and look a darn sight neater, as well as giving the dome a lower profile. I didn't have any 10g brass so I figured 15g stainless would be just as good given all those screws holding it down! The screws are set in a little, to engage at full depth in the thickest part of the bush. Will someone please tell me if I got that wrong, as the bush hasn't been put in yet! If you look very carefully at the picture you'll see the broken tap on the other side as I was cleaning up the one hole that needed a little extra depth after assembly....Lots of Railroad Esperanto, and the Machinemart HSS taps are NOT strong enough, but it's OK, I managed to remove it! Tempus fugit..... 
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redmog
Part of the e-furniture
Not Morgan weather
Posts: 461 
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Post by redmog on Nov 23, 2009 19:19:29 GMT
Time Flies!!!!!! JB. We've been discussing dome bushes and the like recently. modeleng.proboards.com/index.cgi?action=display&board=boiler&thread=4514&page=1#43397Yours looks fine. I turn my dome cover so that I can turn it to fit inside the dome bush, as in the photograph of the above link, giving a shoulder and register around which I wrap some PTFE tape to seal it. It's worked for the last 20 years no trouble. Whats ' Tempus Fugit' got to do with it? Chris
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Post by Deleted on Nov 23, 2009 19:33:55 GMT
Time Flies!!!!!! Whats ' Tempus Fugit' got to do with it? Chris As you said Chris, time flies, and so much to do! JB |
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Post by Shawki Shlemon on Nov 24, 2009 10:09:25 GMT
Have you seen the thread on boilers regarding dome bush JB ?
I would be using SS screws , the thickness of the bush flange at least 1.5 times the diameter of the screws , the number and size of screws depend on the size of the bush . If you specify the PCD of the screws , I can tell you what the OZ code specify in regard the number and sizes of the screws . I know our code does not apply in the mother country but it is a just a guide .
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Post by Deleted on Nov 24, 2009 10:31:02 GMT
Thanks Shawki. I will be substituting SS screws, but I'm happy with the SS cover as it is quite adequate for my purposes.
JB
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Post by Deleted on Nov 26, 2009 13:54:40 GMT
A REAL Disaster, possibly terminal!We got two burners on the foundation ring, just to be sure etc., and we were very happy with the joints everywhere, and this crack suddenly opened up on the throatplate. I cleaned it up and resoldered it, but it opened up again on cooling! Our boiler inspector scratched his head and said he'd never seen anything like it.... Bit of a bummer that! Perhaps I should keep the other side of the boiler tube hot until this side cools down! Now where's my cheque book........ 
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kwil
Part of the e-furniture
Posts: 383
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Post by kwil on Nov 26, 2009 14:06:03 GMT
Do you know [yet] whether it is the silver solder that has failed or [since the joint should be stronger than the parent metal] the copper itself?
It was just a butt joint? Bad music I guess.
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Post by dickdastardly40 on Nov 26, 2009 14:13:51 GMT
Gutted for you!
Hope it can be sorted.
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Post by Deleted on Nov 26, 2009 14:31:32 GMT
I think we will probably try and sort it by putting a strap round it using oxy/acetylene.
JB
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brozier
Part of the e-furniture
Posts: 335
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Post by brozier on Nov 26, 2009 16:04:35 GMT
Hi JB,
It look to me like the barrel has cooled down much quicker than the wrapper. The obvious cause for this is that the wrapper is encased in heat retaining fire bricks and the barrel is waving about in the wind.
I'd suggest laying the assembly on it's side so you can cover both parts with fire brick. I find the kaowool blankets can be handy for wrapping round the barrel.
It does highlight the weakness of that joint design so adding a ring / strap might not be a bad idea....
Cheers
Bryan
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Post by Deleted on Nov 26, 2009 16:12:28 GMT
Hi Brian, I'm inclined to agree with you!
JB
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kwil
Part of the e-furniture
Posts: 383
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Post by kwil on Nov 26, 2009 16:20:00 GMT
Could also be that heat from the firebox passed up the tubes, expanding them pushing the smokebox plate and pulling against the cooler boiler barrel. Bent tubes or split boiler barrel joint and we know which it was.
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Post by Shawki Shlemon on Nov 28, 2009 8:21:11 GMT
In my humble opinion there are two reasons for this , first the but joint is not a strong joint and a few persons here has mentioned this before ( I know it is a published design ) , the second is lack of uniform heating of the boiler before attacking a joint with massive heat . I have built larger boilers than that and never use bricks at all , I use oxy acetylene , heat the entire boiler and then attack the joint ( or side ) while the boiler is hot and let it cool down . clean , inspect and repeat the process for the next joint . Patience is very important .
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Post by Deleted on Nov 28, 2009 9:05:19 GMT
That's sound reasoning Shawki, but is it fixable?
JB
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kwil
Part of the e-furniture
Posts: 383
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Post by kwil on Nov 28, 2009 18:43:54 GMT
The problem with oxy is that the temperature is high but the amount of heat is, surprisingly not as much as you would think. Far better to generally heat overall with a large, 1" / 1.25" propane torch, without too much surrounding brickwork, and whilst everything is hot and it will stay very warm for more than sufficient time, deal with the joint in hand with a 3/4 - 1" pepperpot burner. If the boiler is very big then another pair of hands keeping the overall mass hot whilst working on the joint could be an advantage.
From previous photos it is not your soldering skill that at fault but the inherently poor design of that shell. As I said earlier, wrong music.
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Post by Deleted on Nov 28, 2009 22:06:07 GMT
From previous photos it is not your soldering skill that at fault but the inherently poor design of that shell. As I said earlier, wrong music. That's a very nice thing to say Kwil. Just to update everybody, Marco at Steam Technology has made me a very generous and sympathetic offer for a welded boiler at only 6 weeks lead time which is proving very hard to refuse! JB |
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kwil
Part of the e-furniture
Posts: 383
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Post by kwil on Nov 29, 2009 10:36:35 GMT
What I would wish to know is, it may be welded on the surface but how well does the weld penetrate the joint?
When I was tested for welding certificates I had to section sample joints to prove that they were good welds! Has Marco produced any sample cross section photographs and are they fully CE marked?
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